Conventionally known fuel cell apparatus include a solid oxide fuel cell apparatus using solid electrolyte (solid oxide). The solid oxide fuel cell apparatus includes a fuel cell stack in which a large number of fuel cells are stacked together. Each of the fuel cells is configured, for example, such that a cathode and an anode are provided on respective opposite sides of a plate-shaped solid electrolyte. Air is supplied to the cathode, and fuel gas is supplied to the anode, whereby the fuel gas and oxygen contained in air react chemically with each other via the solid electrolyte, thereby generating electricity. The solid oxide fuel cell apparatus also includes current collectors which are in contact with respective anode and cathode electrically for establishing electrical communication among the fuel cells.
Meanwhile, a thermal cycle which the solid oxide fuel cell apparatus is subjected to in the course of operation or the like causes warpage to the fuel cells. Specifically, because of a poor match in thermal expansion coefficient between an anode and solid electrolyte, in the course of operation, the anode of the fuel cells become warped. As a result, there arises a problem in that reliability in electrical contact between the fuel cells and the current collectors is impaired. In order to solve the problem, according to a known fuel cell apparatus (refer to, for example, Patent Document 1), an end plate having a spherical portion for pressing a fuel cell stack is disposed on each of opposite sides, with respect to a stacking direction, of the fuel cell stack, and a flat spring of metal is disposed between the fuel cells. In such a fuel cell apparatus, the spherical portion of each of the end plates functions to evenly apply surface pressure to the fuel cell stack from the end plate, and an elastic deformation of the flat spring absorbs a dimensional variation of each of the fuel cells, thereby ensuring the reliability of electrical contact between the fuel cells and the current collectors.